10.2.3.2. Indigenous Biodiversity and Protected Areas

Africa occupies about one-fifth of the global land surface and contains about
one-fifth of all known species of plants, mammals, and birds in the world, as
well as one-sixth of amphibians and reptiles (Siegfried, 1989). This biodiversity
is concentrated in several centers of endemism. The Cape Floral Kingdom (fynbos),
which occupies only 37,000 km2 at the southern tip of Africa, has 7,300 plant
speciesof which 68% occur nowhere else in the world (Gibbs, 1987). The
adjacent Succulent Karoo biome contains an additional 4,000 species, of which
2,500 are endemic (Cowling et al., 1998). These floristic biodiversity
hotspots both occur in winter rainfall regions at the southern tip of the continent
and are threatened particularly by a shift in rainfall seasonality (for instance,
a reduction in winter rainfall amounts or an increase in summer rainfall, which
would alter the fire regime that is critical to regeneration in the fynbos).
Other major centers of plant endemism are Madagascar, the mountains of Cameroon,
and the island-like Afromontane habitats that stretch from Ethiopia to South
Africa at altitudes above about 2,000 m (Mace et al., 1998). Montane
centers of biodiversity are particularly threatened by increases in temperature
because many represent isolated populations with no possibility of vertical
or horizontal migration. Several thousand species of plants alone are potentially
affected.

The broad patterns of African zoogeography also are climatically linked, but
the location of concentrations of biodiversity and endemism, at least in the
higher animals, is located in the savannas and tropical forests. World antelope
and gazelle biodiversity (more than 90% of the global total of 80 species) is
concentrated in Africa (Macdonald, 1987). Changes in climate of the magnitude
predicted for the 21st century could alter the distribution range of antelope
species (Hulme, 1996).

This biodiversity forms an important resource for African people. Uses are
consumptive (food, fiber, fuel, shelter, medicinal, wildlife trade) and nonconsumptive
(ecosystem services and the economically important tourism industry).

For a sample of 39 African countries, a median 4% of the continental land surface
is in formally declared conservation areas in southern Africa (MacKinnon and
MacKinnon, 1986). The fraction of landscape that is conserved varies greatly
between countries (from 17% in Botswana to 0% in four countries), as does the
degree of actual protection offered within nominally conserved areas (MacKinnon
and MacKinnon, 1986). A very large fraction of African biodiversity occurs principally
outside of formally conserved areas (especially in central and northern Africa),
as a result of a relatively low rate of intensive agricultural transformation
on the continent. This will no longer be true if massive extensification of
agriculture and clearing of tropical forests occurs in the humid and subhumid
zones, as is predicted to occur in the next century by some land-cover change
models (Alcamo, 1994). Patterns of human pressure, including grazing by domestic
stock, also will be altered and intensified by climate change. Land-use conversion
effects on biodiversity in affected areas will overshadow climate change effects
for some time to come.

In the medium term (~10-20 years), biodiversity of indigenous plants and
animals in Africa is likely to be affected by all of the major environmental
changes that constitute climate change. These include changes in ambient air
temperature, rainfall and air vapor pressure deficit (which combine to cause
altered water balance), rainfall variability, and atmospheric CO2.

Africalike the other continents, though perhaps to a greater degreeis
characterized by ecosystem control through disturbance, such as fire (Bond and
van Wilgen, 1996) and grazing regimes. Changing disturbance regimes will interact
with climate change in important ways to control biodiversityfor instance
through rapid, discontinous ecosystem "switches." For example, changes
in the grazing and fire regime during the past century are thought to have increased
woody-plant density over large parts of southern Africa. Ecosystem switches
are accompanied by drastic species shifts and even species extinction. Subtle
changes in species composition of rich ecosystems such as forests will impact
biodiversity resources. A significant reduction in rainfall or increase in evapotranspiration
in Angola would threaten the Okavango delta wetland in Botswana. Much larger
scale ecosystem switches (e.g., savanna to grassland, forest to savanna, shrubland
to grassland) clearly occurred in the past (e.g., during the climatic amelioration
dating from the last glacial maximum), but diversity losses were ameliorated
by species and ecosystem geographical shifts. The geographical range shifts
recquired to preserve biodiversity into the future will be strongly constrained
by habitat fragmentation and cannot realistically be accommodated by a static
nature reserve network with the low areal coverage evident in Africa.

Theory required to predict the extent and nature of future ecosystem switches
and species geographical shifts in Africa is lacking, and case studies are few.
The response of major vegetation types to changes such as rising atmospheric
CO2 are almost unstudied, although early evidence (Midgley et al., 1999;
Wand et al., 1999) suggests, for example, that these responses may increase
WUE in grass species significantly, which may increase grass fuel load or even
increase water supply to deeper rooted trees. Recent analysis of tree/grass
interactions in savannas suggests that rising atmospheric CO2 may increase tree
densities (Midgley et al., 1999); this kind of ecosystem switch would
have major implications for grazing and browsing animal guilds and their predators.
For southern Africa, between one-quarter and one-third of current reserves were
predicted to experience a biome shift (a major change in the dominant plant
functional types) under the equilibrium climate resulting from a twice-preindustrial
CO2 concentration (Hulme, 1996). In South Africa, increased aridity in the interior
Bushmanland plateau will introduce a desert-like environment to the country
(Rutherford et al., 1999). Analysis for South African conservation areas
(Rutherford et al., 1999) shows potentially large losses of plant species
diversity in this semi-arid region with low landscape heterogeneity.

Thus, the vegetation and animal communities that many reserves aim to conserve
will no longer be within their preferred bioclimatic region. Migration of animals
to conserved areas with more suitable climate (if these exist) will be constrained
by fragmentation of intervening ecosystems and potentially hostile landscapes.
The required rate of migration may be too rapid for unassisted movement of most
plant species, especially over relatively flat landscapes (Rutherford et
al., 1995). Without adaptive and mitigating strategies, the impact of climate
change will be to reduce the effectiveness of the reserve network significantly,
by altering ecosystem characteristics within it and causing species emigrations
or extinctions.

At particular risk of major biodiversity loss are reserves on flat and extensive
landscapes, those in areas where rainfall regime may change seasonality (e.g.,
the southern Cape), those where the tree/grass balance is sensitive to CO2 conditions,
and those where the fire regime may be altered. Species most at risk are those
with limited distribution ranges and/or poor dispersal abilities, habitat specialists
(soil specialists in the case of plants), and those that are responsive to specific
disturbance regimes.

Mitigation and adaptation strategies will be greatly strengthened by a risk-sharing
approach between countries, which could attempt to share the burden of conserving
critical populations in a collaborative way. Part of this risk-sharing approach
could include transboundary nature reserves, where this is appropriate for increasing
connectivity in areas projected to change significantly. The corridor approach
within and between countries would have the added benefit of increasing reserve
resilience to current climate variability and would increase attractiveness
to the tourism industry. Economic incentives, however, may differ across geographic
scales. For the moist tropical forests of Masoala National Park in northeast
Madagascar, economic incentives favor conservation at local and global scales,
although logging provides more profit at a national scale (Kremen et al.,
2000).

A high degree of uncertainty is associated with predictions of the biodiversity
effects of climate change. No systematic analysis of mechanisms of ecosystem
switches, or areas exposed to them, has been carried out. Although fire and
atmospheric CO2 seem to be important determinants of ecosystem structure and
function, little research is available to predict how these factors will interact
with other environmental changes. The effects of CO2 on grass water use may
be an important mitigator of negative effects on productivity for grazer guilds
in much of subtropical Africa. Effects of shifts of disease-prone areas on animal
populations are unstudied.